RF Glow Discharge Plasma Treatment of Graphene Sheets: a Possible Route for the Development of Nanostructured Electrodes in Organic Solar Cells

Graphene sheets are one-atom thick, 2D layers of sp2-bonded carbon atoms, which can be considered as the building blocks for carbon materials such as graphite, carbon nanotubes and fullerene. Considering that graphene has been recently available for experiments1, it is considered as a new material both for fundamental research and potential applications. One of the strategies most used to afford single sheets of graphene relies on the graphite oxide.2-4 Graphite oxide is heavily oxygenated, bearing hydroxyl and epoxide functional groups on their basal planes, making it strongly hydrophilic, which allows its dispersion and swelling in water. This leads to a carbon material partially oxygenated with a high specific surface area. However, the strong tendency of graphene layers to stack between each other due to van der Waals interactions prevents their solubilization in any medium. So, a critical aspect in the graphene manipulation is to maintain the sheets separated. So far, chemical functionalization of graphene has focused on improving its solubility/processability in both water and organic solvents using different soluble groups.5 We demonstrate that the direct fluorination of graphene sheets (GSs) and their subsequent derivatization provides a versatile tool for the preparation and manipulation of graphenes with variable sidewall functionalities. Fluorine in graphene can be efficiently displaced by alkylamino and other functionalities leading to a nucleofilic substitution.6 In particular we propose a novel approach to achieve stable colloidal suspensions of quasi-two-dimensional GSs through rf plasma enhanced chemical vapour deposition. The plasma functionalization of graphene represents a novel approach easy to scale up to industrial applications.